The effects of early deprivation on the psychosocial development of nonhuman primates have been amply documented. Progress has also been made toward describing the effects of different kinds and amounts of social contact on social development. In contrast to the advances that have been made in these problem areas, our knowledge of the specific mechanisms involved in normal social development is surprisingly meager. In the proposed research we are primarily concerned with perceptual- cognitive factors in psychosocial development. Research on newborn monkeys focuses on the formation of an attachment to a specific object, and the processes through which the infant comes to recognize its mother. How do maternal attributes influence the strength and specificity of early filial attachments? What are the equivalence relationships between different sensory channels as reflected in object recognition and in the ability to provide emotional reassurance? In research with older animals we are investigating developmental contrasts in perceptual-cognitive functions within the setting of a social group. We are particularly concerned with the effects of rearing conditions on the amount and complexity of social information that an individual is able to use as a member of a social group.